Browsing by Subject "Compaction"

Now showing 1 - 8 of 8
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    Development of Superpave 5 Asphalt Mix Designs for Minnesota Pavements
    (Minnesota Department of Transportation, 2022-06) Yan, Tianhao; Marasteanu, Mihai; Le, Jia-Liang; Turos, Mugurel; Cash, Kristen
    High field density is desired for improving the durability of asphalt pavements. This research aims to develop Superpave 5 mixtures (more compactable than traditional Superpave mixtures) by using locally available materials to improve the field density in Minnesota. First, previous projects in Minnesota were investigated. The mean and standard deviation of field density in Minnesota were about 93.5% Gmm and 1.5% Gmm, respectively. Significant correlations were identified between field density and mix design indices, i.e., Ndesign, NMAS, and fine aggregate angularity (FAA). Four traditional Superpave mixtures were then selected and modified to Superpave 5 mixtures by adjusting their aggregate gradations while maintaining the asphalt binder content. Laboratory performance tests were performed to check the mechanical properties of the modified mixtures. The results showed it was feasible to design Superpave 5 mixtures (more compactable mixtures) by adjusting aggregate gradations, and the improved compactability of the mixtures did not adversely affect the performance of the mixtures for rutting, stiffness, and cracking resistance. Therefore, Superpave 5 mixtures can increase field density as well as other performances of asphalt pavements if implemented.
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    Experimental and Computational Investigations of High-Density Asphalt Mixtures
    (Minnesota Department of Transportation, 2019-10) Marasteanu, Mihai; Le, Jia-Liang; Hill, Kimberly; Yan, Tianhao; Man, Teng; Turos, Mugurel; Barman, Manik; Arepalli, Uma Maheswar; Munch, Jared
    Compaction of asphalt mixtures represents a critical step in the construction process that significantly affects the performance and durability of asphalt pavements. In this research effort, the compaction process of asphalt mixtures was investigated using a combined experimental and computational approach. The primary goal was to understand the main factors responsible for achieving good density and was triggered by the success of a recently proposed Superpave 5 mix design method. First, a two-scale discrete element method (DEM) model was developed to simulate the compaction process of asphalt mixtures. The computational model was anchored by a fluid dynamics-discrete element model, which is capable of capturing the motion of aggregates in the viscous binder. The model was then calibrated and validated by a series of experiments, which included rheological tests of the binder and a compaction test of the mixture. It was concluded that the compaction process was significantly influenced by the rheological properties of the fine aggregate matrix and by the sphericity of the coarse aggregates. Finally, the mechanical properties of two high-density mixtures were determined and compared with mechanical properties of mixtures used for MnROAD 2017 National road Research Alliance (NRRA) test sections. It was found that the properties of high-density mixtures as a group were not significantly different compared to the properties of conventional mixtures.
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    Investigation of Asphalt Mixtures Compaction Using a Novel Approach Based on Tribology
    (Center for Transportation Studies, University of Minnesota, 2020-12) Yan, Tianhao; Turos, Mugurel; Kumar, Ravi; Marasteanu, Mihai
    Compaction is one of the most important factors that affects the durability of asphalt pavements. Many studies have been focused on developing methods to improve compaction. Previously, the authors found that the addition of small percentages of Graphite Nanoplatelets (GNPs) significantly increase the compactability of asphalt mixture. Traditional viscosity test results show that the increase in compactability is not a result of viscosity reduction, which implies that other mechanisms are responsible for the increase in compactability of GNP modified mixtures. This study investigates the lubricating behavior of the binder. A new test method, referred to as a tribological test, is conducted to evaluate the lubricating behavior of binders modified with different percentages of GNP (0%, 3%, and 6%). To better simulate the roughness of the aggregate surface, the tribological fixture is modified using textured contact surfaces instead of smooth ones. The results of rough surface tribological tests show that the addition of GNPs increases the lubrication behavior of the thin film binder between rough surfaces. It is hypothesized that the increase in compactability can be attributed to the increase in the lubricating behavior of the binder due to the addition of GNP.
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    Low-Vibration Methods of Soil Compaction for Urban Utility Projects: Phase 2
    (1995-04) Sterling, Raymond L.
    This report presents the findings of the second phase of an exploratory project to assess the potential of nonvibratory methods of compaction for utility-related compaction needs. Proposed refinements and additions to existing compaction procedures are based on the use of an alternating flooding and vacuum procedure introduced through a pipe or series of pipes embedded in the soil. This process had been demonstrated in early Phase I laboratory tests to give better results than flooding alone for granular soils. Phase II laboratory and field tests produced compaction results ranging from an acceptable level of compaction to an unacceptable level. The flood/vacuum method appeared to work best in well-graded granular materials including some, but not an excessive amount of, fine particles. The cycle times for flooding and vacuum removal of the water appeared to be too long for practical use. The flood/vacuum technique by itself, or without reasonable levels of static compaction, does not appear to be a viable technique for field use. It appears that results from the technique could be significantly approved by adding mechanical disturbance of the backfill material or vibration energy to the flooding cycle.
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    Rapid Determination of Field Properties of Compacted Materials
    (Center for Transportation Studies, University of Minnesota, 1997-12) Sterling, Raymond L.
    The report describes the results of a limited investigation into the technical progress and acceptance of techniques for field determination of the engineering properties of compacted materials. Although some of these techniques have been investigated for several decades, few are in common use. The reports discusses the benefits and limitations of the principal techniques and concentrates on acceptance issues for their use in practice.
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    Rheology of Granular-Fluid Systems and Its Application in the Compaction of Asphalt Mixtures
    (2019-04) Man, Teng
    The United States has more than 2.7 million miles of paved roads, of which 94\% are surfaced with asphalt pavement. The resilience and durability of asphalt materials have important consequences for transportation safety. Previous research showed that the porosity, i.e. the fraction of air voids in an asphalt pavement, which is largely influenced by the compaction during the installation process, has a significant influence on the durability of installed asphalt pavements. Therefore, understanding the compaction process of asphalt mixtures has become an essential topic of research. However, the existing modeling approaches are mostly phenomenologically based. Very few studies have focused on developing a physics-based predictive model for the compaction of asphalt mixtures. The development of a physics-based computational model is complicated by the complexity and variability of the asphalt mixture. Asphalt mixtures consist of (1) aggregates (sand, pebbles, and rocks) up to 3\ cm in size, (2) fine aggregate mixtures or FAM consisting of the sand portion of the aggregates, asphalt binder, and other additives coats. During the compaction process, the FAM surrounds the coarser aggregates and ultimately as the mixture cools and solidifies, binds them like glue. The details of each component vary considerably across the country. Part of the difficulty in modeling the compaction of such a complex multiphase mixture is to developing reliable rheology for the constitutive behavior of the mixture. In this study, we developed a multi-scale discrete element method (DEM) model for compaction of asphalt mixtures. The model is anchored by the representation of the asphalt as a two-phase mixture: (1) liquid-like FAM and (2) individual gravel particles. On the macroscopic level, only coarse (large) aggregates are considered in the simulation as non-spherical particles. The interaction between these aggregates is mediated both by the coarse particle properties and the properties of the interstitial fluid-like slurry FAM. We derive the dependence of the FAM rheology to the fluid properties of the asphalt binder and the solid properties of the finer particles using discrete element model (DEM) simulations. We use larger scale DEM simulations with coarse aggregates and the modeled FAM to model the gyratory compaction process of hot mixed asphalt with different viscosity of asphalt binder and different aggregate size distributions. The results of the thesis are comprised of three primary components described in this thesis: (1) the small scale model of particles and fluid which provide more macroscale and particle scale information about slurry flow behavior; (2) the larger multi-scale model framework of the asphalt compaction process itself as a process. The results can provide a systematic method for improving the mix design of asphalt mixtures and the compaction procedures toward a more efficient compaction process.
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    Soil Compaction in Upper Midwestern Crop Production
    (2024-09-12) Bolwerk, Gabrielle; DeJong-Hughes, Jodi; Daigh, Aaron
    This fact sheet explains the causes, effects, diagnosis, and management of soil compaction in upper Midwestern cropping systems.
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    Structure-property relationships of solids in pharmaceutical processing
    (2012-11) Chattoraj, Sayantan
    Pharmaceutical development and manufacturing of solid dosage forms is witnessing a seismic shift in the recent years. In contrast to the earlier days when drug development was empirical, now there is a significant emphasis on a more scientific and structured development process, primarily driven by the Quality-by-Design (QbD) initiatives of US Food and Drug Administration (US-FDA). Central to such an approach is the enhanced understanding of solid materials using the concept of Materials Science Tetrahedron (MST) that probes the interplay between four elements, viz., the structure, properties, processing, and performance of materials. In this thesis work, we have investigated the relationships between the structure and those properties of pharmaceutical solids that influence their processing behavior. In all cases, we have used material-sparing approaches to facilitate property assessment using very small sample size of materials, which is a pre-requisite in the early stages of drug development when the availability of materials, drugs in particular, is limited. The influence of solid structure, either at the molecular or bulk powder levels, on crystal plasticity and powder compaction, powder flow, and solid-state amorphization during milling, has been investigated in this study. Through such a systematic evaluation, we have captured the involvement of structure-property correlations within a wide spectrum of relevant processing behaviors of pharmaceutical solids. Such a holistic analysis will be beneficial for addressing both regulatory and scientific issues in drug development.